The present disclosure relates to an apparatus and method for refining molten aluminum alloys. It finds particular application in conjunction with a flux injection assembly configured to introduce flux to the molten aluminum alloy as it flows through a trough, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications.
Molten metals such as aluminum and aluminum alloys include trace amounts of impurities that are desired to be removed during refinement. In known refinement processes, aluminum is melted within a furnace and then transferred to a casting machine for metal formation. The aluminum is typically transferred from the furnace to the casting machine through a trough. The molten aluminum flows into the trough at an inlet and through the trough to exit at an outlet in a substantially continuous manner. In many instances, the trough includes a degassing treatment assembly and/or a filter that are intended to remove at least a portion of the impurities within the molten aluminum. Some of the impurities include dissolved hydrogen gas, particulates such as oxides, carbides, borides, alumina, magnesia, and various other elements such as dissolved alkali metals (sodium (Na), lithium (Li) and Calcium (Ca)). These impurities may cause undesirable effects in the casting process and to the properties of the finished product.
The treatment process generally utilized a flux injection mechanism that is configured to introduce a flux within the molten aluminum. Generally, flux comprises chlorine gas or mixtures of chlorine gas with an inert gas such as argon that, when combined, are known to assist with the removal of impurities from the molten aluminum. One such example of flux is marketed as PROMAG™ by Pyrotek, Inc of Spokane, Wash. Chlorine gas and chlorine salts are known to be effective in converting the alkali metals to salts which coalesce and rise to the surface of the molten material with the assistance of the inert gas. In particular, hydrogen gas diffuses into the inert gas bubbles and is removed as the particulate coalesces around the gas bubbles and rises to the top of the molten aluminum alloy. The flux and impurities form dross or a waste-by-product which is skimmed off periodically or captured in a downstream filter. Generally, the chlorine and/or chlorine salts are removed with the dross. However, there has been pressure to eliminate the use of chlorine gas in applications such as these because of the environmental damage and burden of handling.
An in-line flux injection mechanism is disclosed in U.S. Pat. No. 3,767,382, which utilizes chlorine and/or chlorine salts discloses a known process of refining aluminum. Additionally, an apparatus and process for in-line aluminum treatment is disclosed in U.S. Pat. No. 8,025,712, which is incorporated by reference herein. These mechanisms disclose a process for refining molten aluminum and molten aluminum alloys that utilizes various chambers including at least one dispenser having an elongated rotating shaft attached to an impeller. The impellers are adapted to rotate within the molten aluminum as flux is discharged through or at the rotating shaft and distributed by the impeller within the chamber. The impeller and rotating shaft are particularly utilized to distribute the flux within the molten alloy in a manner sufficient to provide a broad distribution of the flux within the molten alloy to chemically interact with a high percentage of the impurities therein while utilizing a minimum amount of chlorine gas or salts. The impurities then rise to the surface of the molten aluminum alloy and can be removed.